Light emitting elements, such as light emitting diodes (LEDs), may have operating voltages of less than 4 V. If they are to be supplied by line voltage (or mains voltage), they may need to be connected in series or be driven by switching power supplies. However, switching power supplies are complex and may introduce electromagnetic interference.
Light emitting elements, such as LEDs, may have very short turn-on times and turn-off times which may result in flicker when they are operated with alternating current or a pulse width modulated (PWM) current. Flicker may be reduced by a smoothing capacitor for the current. However, the smoothing capacitor may need to be rated at the line voltage and capacitors with a high capacity are required because of the low frequency of the line voltage. To keep costs low, electrolytic capacitors may be used as smoothing capacitors. However, electrolytic capacitors may have a limited lifetime, especially when they are operated at high temperatures, and may be difficult to miniaturize.